1. Field of the Invention
This invention relates in general to pipe joints and in particular to a method for assembling pipe joints so that the down-hole circumferential orientation of a pipe in a pipe string can be determined by the orientation of any other pipe in the same pipe string.
2. Description of Related Art
In a pipe string having a series of joints, each joint having a pin member threadingly connected to a coupling member, it is often desirable to know the circumferential orientation of one pipe in the pipe string relative to another pipe in the string. One method of accomplishing this result is to control the threading process of each pin member and each coupling member so that the relative orientation of one pipe to another is known when any pin member is connected to any coupling member. The circumferential orientation of one pipe relative to another is demonstrated by an alignment mark placed on each pin member and coupling member during the threading process.
U.S. Pat. No. 4,962,579 teaches a method for visually determining on the rig floor if a joint is properly made up with the right amount of torque. A registry mark is placed on the exterior of the first pipe section for proper axial engagement of the pin member with the coupling or box member. The position is determined by finite element analysis.
U.S. Pat. No. 5,212,885 shows a method for achieving proper sealing positioning and proper make up torque of threaded pipe sections. The method is described in column 4, lines 33-44 of the specification. If the face of the box member is properly positioned relative to a triangle mark on the pipe section, make up is terminated. If the face has not reached edge of the triangle mark, torque is increased until either the face progresses into the body of the triangle mark or until maximum torque occurs.
U.S. Pat. No. 4,614,120 shows a method for determining proper make-up torque for pipe joints. A reference mark is set on the male element and on the female element. A grease is applied to the joint and the joint is made up using sufficient torque to cause one element to rotate with the respect to the other element. The joint is torqued until one element reaches a predetermined angle beyond the point where the reference marks are facing each other. This operation is repeated with a determination being made of the range of torques to be applied to the joint with a particular grease being utilized.
U.S. Pat. No. 5,661,888 shows an apparatus for positing two threaded pipes within a target range of relative axial positions. The device supposedly offers advantages over using visual xe2x80x9cbench marksxe2x80x9d placed on the pin and box members. The device includes a sensor and calibrating device for positioning the sensor a calibrated distance from the end of one of the pipes. A signal generator generates a signal once the sensor head indicates that the relative axial position of the pipes are within the target range desired.
Each of the above references primarily deal with methods for properly torqueing a threaded pipe connection. As such, they do not teach the current method for assembling a series of pipe joints so that the circumferential orientation of one pipe in the pipe string can be determined by reference to another pipe in the string.
A need continues to exist for a simple and economical method for indexing a string of pipe containing a plurality of joints by which the circumferential orientation of one pipe in the pipe string can be determined by reference to another pipe in the string.
A need also exists for such a method which does not require elaborate gaging systems or electronic sensors or sensing systems.
A need also exists for such a method which does not add appreciably to the costs of the pipe threading process, which is simple to implement, and which is reliable in operation.
The method of assembling pipe joints according to the present invention allows the circumferential orientation of a pipe in a pipe string to be determined relative to that of another pipe in the same pipe string. The pipe string is made up of a series of joints, each joint having a coupling member and at least one pin member which are threadingly connected.
Before machining threads on the pin members or the coupling members, a pin marking gage and a coupling marking gage are prepared. The two gages are adapted to threadingly engage each other. A pin gage alignment mark is scribed on the pin marking gage, and a coupling gage alignment mark is scribed on the coupling marking gage. When the pin marking gage and the coupling marking gage are threadingly connected in a first contact position, the pin gage alignment mark and the coupling gage alignment mark are separated by a circumferential offset which represents the amount of rotation remaining to put the gages in a fully engaged position.
A pin alignment mark is placed on each pin member, and a coupling alignment mark is placed on each coupling member. A plurality of threads is machined on an exterior annular surface of the pin member to an initial pin depth. The coupling marking gage is threadingly connected to the pin member, and a circumferential offset between the coupling gage alignment mark and the pin alignment mark is recorded. Based on the circumferential offset, the pin member is again machined, thus altering the initial pin depth of the threads so that the pin alignment mark will align with the coupling gage alignment mark when the gage and the pin member are connected in the first contact position.
A plurality of threads is machined on an interior annular surface of the coupling member to an initial coupling depth. The pin marking gage is threadingly connected to the coupling member, and a circumferential offset between the pin gage alignment mark and the coupling alignment mark is recorded. Based on the circumferential offset, the coupling member is again machined, thus altering the initial coupling depth so that the coupling alignment mark will align with the pin gage alignment mark when the gage and the coupling member are connected in the first contact position.
After machining threads on each pin member and each coupling member according to the preceding method, the pipe string is assembled by connecting each pin member to a coupling member. As each joint is assembled, every pin alignment mark in the pipe string is aligned with all of the other pin alignment marks as well as all of the coupling alignment marks. The alignment of the marks along the pipe string allows determination of the orientation of any pipe in the string by observing the orientation (indicated by the alignment marks) of any other pipe in the string.
Additional objects, features, and advantages will be apparent in the written description which follows.